U.S. patent application number 16/085530 was filed with the patent office on 2019-12-19 for furoic acid preparation method.
This patent application is currently assigned to Universite de Lille. The applicant listed for this patent is ALMA MATER STUDIORUM - UNIVERSITA' DI BOLOGNA, CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE, ECOLE CENTRALE DE LILLE, UNIVERSITE DE LILLE. Invention is credited to Fabrizio CAVANI, Franck DUMEIGNIL, Sebastien PAUL, Francesco SANTARELLI, Robert WOJCIESZAK.
Application Number | 20190382361 16/085530 |
Document ID | / |
Family ID | 55863070 |
Filed Date | 2019-12-19 |
United States Patent
Application |
20190382361 |
Kind Code |
A1 |
PAUL; Sebastien ; et
al. |
December 19, 2019 |
FUROIC ACID PREPARATION METHOD
Abstract
A method is for the preparation of furoic acid or of one of its
derivatives of formula (I): ##STR00001## in which R.sub.1, R.sub.2,
R.sub.3 and R.sub.4 represent, independently of each other, a
hydrogen atom, a linear or branched C.sub.1-C.sub.6 alkyl group, a
--C(.dbd.O)--H group or a --COOH group, by heterogeneous catalytic
oxidation of furfural or a derivative thereof of formula (II). The
oxidation is carried out in the presence of a supported catalyst
based on gold nanoparticles, and in a non-alkaline aqueous medium.
A composition useful in the method includes at least furfural and
supported gold nanoparticles.
Inventors: |
PAUL; Sebastien; (Thun Saint
Amand, FR) ; SANTARELLI; Francesco; (Senigallia,
IT) ; WOJCIESZAK; Robert; (Lille, FR) ;
DUMEIGNIL; Franck; (Fretin, FR) ; CAVANI;
Fabrizio; (Modena, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UNIVERSITE DE LILLE
ECOLE CENTRALE DE LILLE
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
ALMA MATER STUDIORUM - UNIVERSITA' DI BOLOGNA |
Lille
Villeneuve d'Ascq
Paris
Bologna |
|
FR
FR
FR
IT |
|
|
Assignee: |
Universite de Lille
Lille
FR
Ecole Centrale de Lille
Villeneuve d'Ascq
FR
Centre national de la recherche scientifique
Paris
FR
Alma Mater Studiorum - Universita' di Bologna
Bologna
IT
|
Family ID: |
55863070 |
Appl. No.: |
16/085530 |
Filed: |
March 16, 2017 |
PCT Filed: |
March 16, 2017 |
PCT NO: |
PCT/EP2017/056264 |
371 Date: |
September 14, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01J 35/0066 20130101;
B01J 35/1014 20130101; B01J 21/066 20130101; C07D 307/68 20130101;
B01J 35/006 20130101; B01J 23/52 20130101; B01J 21/02 20130101;
B01J 35/0013 20130101; B01J 35/1009 20130101 |
International
Class: |
C07D 307/68 20060101
C07D307/68; B01J 23/52 20060101 B01J023/52; B01J 21/06 20060101
B01J021/06; B01J 21/02 20060101 B01J021/02; B01J 35/00 20060101
B01J035/00; B01J 35/10 20060101 B01J035/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 16, 2016 |
FR |
1652217 |
Claims
1. A method for the preparation of furoic acid or of one of its
derivatives of formula (I): ##STR00004## in which R.sub.1, R.sub.2,
R.sub.3 and R.sub.4 represent, independently of each other, a
hydrogen atom, a linear or branched C.sub.1-C.sub.6 alkyl group, a
--C(.dbd.O)--H group or a --COOH group, provided that at least one
of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is a --COOH group, by
heterogeneous catalytic oxidation of furfural or a derivative
thereof of formula (II): ##STR00005## in which R' 1, R'2, R'3 and
R'4 represent, independently of each other, a hydrogen atom, a
linear or branched C.sub.1-C.sub.6 alkyl group or a --C(.dbd.O)--H
group, provided that at least one of the R' 1, R'2, R'3 and R'4
groups is a --C(.dbd.O)--H group, wherein the oxidation is carried
out in the presence of a supported catalyst based on gold
nanoparticles and in a non-alkaline aqueous medium.
2. The method according to claim 1, wherein R.sub.1 and R.sub.4 are
each a --COOH group, and R.sub.2 and R.sub.3 are hydrogen.
3. The method according to claim 1, wherein R.sub.4 is --COOH
group, and R.sub.1, R.sub.2, and R.sub.3 are hydrogen.
4. The method according to claim 1, wherein the non-alkaline
aqueous medium is a non-alkaline pH medium having a pH of less than
8.
5. The method according to claim 1, wherein the aqueous medium is
devoid of organic solvent.
6. The method according to claim 1, wherein the aqueous medium
consists of water as a solvent medium.
7. The method according to claim 1, the method comprising: (a)
providing a non-alkaline aqueous solution containing at least one
furfural derivative of formula (II); (b) contacting the derivative
of formula (II) of the medium (a) with gaseous oxygen in the
presence of at least a catalytically-effective amount of supported
gold nanoparticles and under non-alkaline conditions conducive to
the oxidation of the furfural derivative of formula (II) to the
furoic acid derivative of formula (I).
8. The method according to claim 1, wherein the oxidation is
carried out under a partial pressure of oxygen of between 510.sup.5
Pa and 2010.sup.5 Pa.
9. The method according to claim 1, wherein the oxidation is
carried out at a temperature between 70.degree. C. and 150.degree.
C.
10. The method according to claim 1, wherein the catalyst is gold
supported on zirconium dioxide or on hydrotalcite.
11. The method according to claim 1, wherein the catalyst is gold
supported on hydrotalcite.
12. The method according to claim 1, wherein the catalyst is gold
supported on zirconium dioxide.
13. The method according to claim 12, wherein the percentage by
weight of gold in the catalyst Au/ZrO.sub.2 for the oxidation of
furfural is between 1% and 7% by weight.
14. The method according to claim 13, wherein zirconium dioxyde,
used as a support, has a specific surface of less than or equal to
10 m.sup.2/g.
15. The method according to claim 12, wherein the furfural/Au molar
ratio for the oxidation of furfural is between 6 and 34.
16. The method according to claim 11, wherein the percentage by
weight of gold in the Au/hydrotalcite catalyst for the oxidation of
furfural is between 1% and 3% by weight.
17. The method according to claim 16, wherein the hydrotalcite,
used as a support, has a specific surface less than or equal to 10
m.sup.2/g.
18. The method according to claim 11, wherein the furfural/Au molar
ratio for the oxidation of furfural is between 22 and 50.
19. The method according to claim 1, wherein the size of the gold
nanoparticles in the catalyst for the oxidation of furfural is
between 3 nm and 15 nm.
20. The method according to claim 1, wherein the method is
implemented in continuous mode or in batch mode.
21. A composition comprising at least furfural and supported gold
nanoparticles.
22. The composition according to claim 21, further comprising a
furfural derivative of formula (II).
23. The composition according to claim 21, wherein the composition
is non-alkaline.
Description
PRIORITY AND CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the U.S. National Phase Application
under 35 U.S.C. .sctn. 371 of International Application No.
PCT/EP2017/056264, filed Mar. 16, 2017, designating the U.S. and
published as WO 2017/158106 A1 on Sep. 21, 2017, which claims the
benefit of French Application No. FR 1652217, filed Mar. 16, 2016.
Any and all applications for which a foreign or a domestic priority
is claimed is/are identified in the Application Data Sheet filed
herewith and is/are hereby incorporated by reference in their
entireties under 37 C.F.R. .sctn. 1.57.
FIELD
[0002] The present invention relates to furoic acid preparation
methods.
SUMMARY
[0003] The present invention relates to a heterogeneous catalytic
method for the preparation of furoic acid or a derivative thereof
from furfural or one of its derivatives in the liquid phase.
DETAILED DESCRIPTION
[0004] The present invention relates to a heterogeneous catalytic
method for the preparation of furoic acid or a derivative thereof
from furfural or one of its derivatives in the liquid phase.
[0005] Furoic acid (also known as 2-furoic acid, or
furan-2-carboxylic acid, or alpha-furoic acid) is an important
compound for industry and may be used in various fields of
application.
[0006] In particular, furoic acid may be used as a preservative in
pasteurization and sterilization steps in the field of food, thus
acting as a bactericidal and fungicidal agent. It may also be used
as a flavoring agent.
[0007] This compound may be useful in the preparation of nylons in
the field of biomedical research.
[0008] Furoic acid also provides furoic acid esters and is
frequently used as an intermediate in the chemical, pharmaceutical
and agrochemical industries.
[0009] Finally, it may eventually play an important role in the
field of optical technologies because the polar organic crystals
that it forms in the solid state could be key elements of future
photonic technologies allowing the storage of images and
information (Uma et al., Optik--International Journal for Light and
Electron Optics, 2013, 124(17), 2754-2757).
[0010] Among furoic acid derivatives, mention may be made, in
particular, of 2,5-furanedicarboxylic acid (also known by the
abbreviation FDCA) which may be particularly useful in
polymerization reactions in order to obtain, for example,
polyesters, polyamides and polyurethanes. It may also be used in
pharmacology.
[0011] Furoic acid may also be easily hydrogenated to form
tetrahydrofuric acid, which is a very important intermediate in the
pharmaceutical industry.
[0012] There is therefore a real interest in an
economically-advantageous method for the preparation of furoic acid
derivatives.
[0013] One conventional approach is to oxidize the furfural in an
alkaline medium in the presence of a catalyst. It should be noted
that the use of an alkaline medium is necessary to achieve good
catalytic performance in the oxidation reaction.
[0014] As an illustration of this approach may be mentioned, in
particular, the alkali oxidation of furfural with the aid of metal
catalysts in the presence of gaseous oxygen (O.sub.2) (Tian et al.,
Molecules, 2008, 13(4), 948-957; Harrisson et al., Org Synth.,
1956, 36, 36, and the document JP26001111B4 of Terai et al., or
with the help of chromate salts (Hurd et al., 1. Am. Chem. Soc.,
1933.55(3), 1082-1084, and Chakraborty et al., Synthetic
Communications, 1980, 10(12), 951-956), or in the presence of
hydrogen peroxide (H.sub.2O.sub.2) (Corma et al. Chem. Rev., 2007,
107(6), 2411-2502) or alternatively carbon-supported Pt--Pb
bimetallic catalysts (Corma et al., Chem Rev., 2007, 107(6),
2411-2502); Verdeguer et al., J. Chem. Biotechnol., 1994, 61,
97-102, and Verdeguer et al., J. Chem. Biotechnol., 1994, 112,
1-11).
[0015] Although these methods lead, for the most part, to high
yields of furoic acid salts, they are unfortunately not totally
satisfactory.
[0016] Thus, they have the major drawback of requiring at least one
separation and conversion step subsequent to the oxidation step in
order to obtain furoic acid free of its alkaline salt. This
approach therefore leads to the production of large quantities of
salts that are generally of little or no value.
[0017] It has also been shown that the metal catalysts used are
easily poisoned during this step, making them inactive. In
addition, the leaching of metal particles responsible for a gradual
deactivation of the catalysts is also very often noted.
[0018] It has therefore been noted that the need to carry out the
reaction in an alkaline medium has the undesirable side effect of
deactivating the catalyst, in particular because of the degradation
of the catalyst support.
[0019] Thus, in industrial practice, furoic acid is synthesized
using AgO/Cu.sub.20 catalysts. However, such a method suffers from
the need for a high catalyst load, the use of a diluted medium, and
the existence of side reactions. Furfural undergoes not only
oxidation to furoic acid, but also secondary reactions resulting
from cleavage of the furoic cycle. In addition, the catalyst must
be periodically regenerated insofar as the Cu.sub.2O phase is not
stable.
[0020] Another approach to the chemical synthesis of furoic acid
imposes a preliminary Canizzaro reaction from furfural in an
aqueous NaOH solution to obtain furfuryl alcohol and sodium
2-furanecarboxylate. The next step is the reaction of sodium
2-furanecarboxylate with sulfuric acid to obtain furoic acid. The
major disadvantage of this method is the limitation of the
theoretical yield of furoic acid to 50% and the large-scale
generation of sodium hydrogen sulphate which must be removed from
the reaction mixture.
[0021] Furoic acid may also be synthesized via biotechnological
methods (Perez et al., African Journal of Biotechnology, 2009,
8(10), 2279-2282, Eilers et al., Planta, 1970, 94, 253-264; Luna et
al., Rev. Mex. Ciencias Farmaceuticas, 1997, 28, 17-19, and the
documents CU22371A1 and WO9308293A1) using the action of certain
microorganisms or fungi among which one may cite mushrooms such as
those of the species Neurospora crassa and Neurospora ascospora,
yeasts such as Saccharomyces cerevisiae, and bacteria such as those
of the genus Acetobacter, Bacillus, Zooglea, Nocardia and
Pseudomonas.
[0022] Thus, by way of example, furoic acid may be prepared by
oxidation of furfural using a biocatalytic microbial preparation
with Nocardia coraHina B-276 (Perez et al., African Journal of
Biotechnology, 2009, 8(10), 2279-2282). Experiments involving this
microbial conversion resulted in high yields, i.e. 88% from
furfural. The oxidation with Nocardia corallina was considered to
be interesting insofar as the use of most other microorganisms
leads to the production of two oxidation products, namely the
corresponding acid and alcohol. In addition, no destruction of the
furan cycle was observed. However, as explained below, drawbacks
remain.
[0023] The methods currently considered for preparing furoic acid
from furfural therefore do not give complete satisfaction. In the
case of biotechnological methods, the main drawbacks are the
complexity of implementation of the method, the separation of the
final products from the mixture of reagents and also the need to
use substrates of high purity and a very diluted medium. In
addition, in the case of the aforementioned Nocardia coraHina B-276
cells, the yield of furoic acid is only 88% and is obtained after 8
hours of reaction.
[0024] The most important drawbacks of the existing chemical
methods are related, in particular, to the need to work in an
alkaline medium. As mentioned above, this constraint has the
undesirable effect, on the one hand, of requiring a subsequent
treatment of secondary and/or intermediate products while, on the
other hand, of affecting the stability of some of the
catalysts.
[0025] There is, therefore, a particular interest for a
heterogeneous catalysis method without the aforementioned
drawbacks.
[0026] Thus, one of the objectives of the invention is to propose a
method in heterogeneous catalysis, making it possible to directly
produce furoic acid or one of its free derivatives in water (and
not in the form of alkaline salt) with a very high yield.
[0027] Another objective of the invention is to provide a
heterogeneous catalysis method that does not require working in an
alkaline medium, and thus makes it possible to overcome the
phenomenon of degradation of the catalyst support and the loss of
metal residues generally encountered under alkaline conditions.
[0028] Another object of the present invention is to provide a
heterogeneous catalysis method for obtaining high yields of furoic
acid and advantageously in a reduced reaction time.
[0029] Another object of the present invention is to provide a
method using a heterogeneous catalyst that may be easily recycled
without requiring prior treatment.
[0030] Thus, the present invention relates to a method for
preparing furoic acid or a derivative thereof of formula (I):
##STR00002##
in which R.sub.1, R.sub.2, R.sub.3 and R.sub.4 represent,
independently of each other, a hydrogen atom, a linear or branched
C.sub.1-C.sub.6 alkyl group, a --C(.dbd.O)--H group or a --COOH
group,
[0031] provided that at least one of R.sub.1, R.sub.2, R.sub.3 and
R.sub.4 groups is a COOH group,
[0032] by heterogeneous catalytic oxidation of furfural or one of
its derivatives of formula (II):
##STR00003##
in which R'.sub.1, R'.sub.2, R'.sub.3 and R'.sub.4 represent,
independently of one another, a hydrogen atom, a linear or branched
C.sub.1-C.sub.6 alkyl group or a --C(.dbd.O)--H group,
[0033] provided that at least one of R'.sub.1, R'.sub.2, R'.sub.3
and R'.sub.4 groups is a --C(.dbd.O)--H group,
[0034] characterized in that the oxidation is carried out in the
presence of a supported catalyst based on gold nanoparticles and in
a non-alkaline aqueous medium.
[0035] For the purposes of the present invention, the term
"oxidation" means the conversion of at least one aldehyde
--C(.dbd.O)--H function included in formula (II) into at least one
carboxylic --COOH function included in formula (I).
[0036] In the context of the present invention, a non-alkaline
aqueous medium (or non-basic aqueous medium) denotes a non-alkaline
pH medium, i.e. a pH of less than 8 and preferably not more than
6.
[0037] According to a preferred embodiment, this aqueous medium is
devoid of organic solvent.
[0038] According to a particularly preferred embodiment, this
aqueous medium consists of water as a solvent medium.
[0039] In the context of the present invention, a C.sub.1-C.sub.6
alkyl group denotes an alkyl group comprising from 1 to 6 carbon
atoms. Such an alkyl group may be linear or branched and may be
selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl,
tert-butyl, pentyl, hexyl.
[0040] According to a particular embodiment, the method according
to the invention makes it possible to obtain a furoic acid
derivative of formula (I) in which at least two of the R.sub.1,
R.sub.2, R.sub.3 and R.sub.4 groups represent a --COOH group.
[0041] Thus, according to this embodiment, the method according to
the invention may lead to the production of a furoic acid
derivative of formula (I) in which R.sub.1 and R.sub.2, or R.sub.1
and R.sub.3, or R.sub.1 and R.sub.4, or R.sub.2 and R.sub.3 each
represent a --COOH group, while the other two remaining groups
represent, independently of one another, a hydrogen atom or a
linear or branched C.sub.1-C.sub.6 alkyl group, preferably a
hydrogen atom.
[0042] According to a preferred embodiment, the method according to
the invention makes it possible to obtain a furoic acid derivative
of formula (I) in which R.sub.1 and R.sub.4 each represent a --COOH
group, and R.sub.2 and R.sub.3 represent a hydrogen atom. It is
then 2,5-furan dicarboxylic acid.
[0043] According to another embodiment, the method according to the
invention makes it possible to obtain a furoic acid derivative of
formula (I) in which R.sub.1 represents a --C(.dbd.O)--H group or a
--COOH group; R.sub.2 and R.sub.3 represent, independently of one
another, a hydrogen atom or a linear or branched C.sub.1-C.sub.6
alkyl group; and R.sub.4 is a --COOH group.
[0044] According to another particular embodiment, the method
according to the invention makes it possible to obtain a furoic
acid derivative of formula (I) in which only one of the R.sub.1,
R.sub.2, R.sub.3 and R.sub.4 groups is a --COOH group, while the
other three remaining groups are, independently of each other, a
hydrogen atom or a linear or branched C.sub.1-C.sub.6 alkyl
group.
[0045] According to another preferred embodiment, the method
according to the invention makes it possible to obtain a furoic
acid derivative of formula (I) in which R.sub.4 is a --COOH group,
and R.sub.1, R.sub.2, and R.sub.3 represent an atom of hydrogen. It
is then furoic acid itself.
[0046] Admittedly, oxidation methods of furfural using catalysts
based on gold nanoparticles supported on zirconium dioxide
(ZrO.sub.2) or cerium dioxide (CeO.sub.2) in the presence of
methanol are well known, but these reactions, although carried out
in the absence of a base (non-alkaline medium), lead to methyl
furoate and not directly to furoic acid (Signoretto et al.,
Catalysts, 2013, 3, 656-670, Manzoli et al., Journal of Catalysis,
2015, Vol 330, 465-473 and Pinna et al., Catalysis Today, 2013,
Volume 203, 196-201).
[0047] As is apparent from the experimental part which follows, the
method according to the invention is particularly advantageous in
several ways.
[0048] More specifically, it provides access to a very high yield
of furoic acid or one of its derivatives, namely a yield of the
order of 98%.
[0049] The conversion of a furfural derivative of formula (II) into
its oxidation derivative of formula (I), in this case furoic acid
for furfural, is carried out in a single step in the presence of
gaseous oxygen in presence of a supported catalyst based on
gold.
[0050] The method according to the invention makes use of catalytic
formulations that are very effective and reactive in a non-basic
medium.
[0051] This advantage allows direct access to the acid form of the
compound of formula (II) and not to its alkaline salt. The
subsequent step of converting this salt into acid is no longer
required and the production of a large amount of salts that are of
little or no value may be avoided.
[0052] In addition, the inventors have discovered that no leaching
phenomenon occurs during catalytic tests with this type of
catalyst
[0053] In fact, the gold contents in the solutions after 4 hours
and 15.5 hours of reaction were measured by ICP-OES (measurements
by induced plasma analysis--optical emission spectrometry). They
were found to be below the detection limit of the analyzer
indicating that the passage of gold from the solid catalyst to the
solution (a phenomenon known as leaching) does not occur for
catalysts that are suitable for the present invention.
[0054] According to an alternative embodiment, the method of the
invention comprises at least the steps of: [0055] (a) having a
non-alkaline aqueous solution containing at least one furfural
derivative of formula (II); [0056] (b) contacting the derivative of
formula (II) of the medium (a) with gaseous oxygen in the presence
of at least a catalytically-effective amount of supported gold
nanoparticles and under non-alkaline conditions that are conducive
to the oxidation of the furfural derivative of formula (II) to the
furoic acid derivative of formula (I).
[0057] Preferably, step (b) is carried out with stirring and under
a pressure of the order of 15 bars (1510.sup.5 Pa) by heating the
assembly to a temperature between 70.degree. C. and 150.degree. C.,
preferably between 90.degree. C. to 120.degree. C., more preferably
110.degree. C.
[0058] The time (or duration) of reaction is adjusted to obtain a
yield of furoic acid derivative of formula (I) equal to at least
80%.
[0059] This reaction time may advantageously be only 1 to 4
hours.
[0060] According to a particular embodiment, the catalyst used is
gold supported on zirconium dioxide.
[0061] According to another particular embodiment, the catalyst
used is gold supported on hydrotalcite.
[0062] Advantageously, as illustrated in the experimental part
below, the method according to the invention makes it possible to
obtain a furoic acid derivative of formula (I) and more
particularly furoic acid with a high conversion, yield, selectivity
and carbon balance.
[0063] For the purpose of the present invention, the terms
"conversion rate" or "conversion" denote the ratio of the number of
moles of furfural derivative of formula (II) reacted, divided by
the number of moles of the furfural derivative of formula (II)
initially introduced.
[0064] By "selectivity" is meant the ratio of the number of moles
of furoic acid derivative of formula (I) obtained at the end of the
reaction divided by the number of moles of the furfural derivative
of formula (II) reacted.
[0065] By "yield" is meant the ratio of the number of moles of
furoic acid derivative of formula (I) obtained at the end of the
reaction divided by the number of moles of the furfural derivative
of formula (II) initially introduced.
[0066] By "carbon balance" is meant the ratio of the number of
carbon atoms present in the reactor at the end of the reaction
divided by the number of carbon atoms initially present in the
reactor.
[0067] Another advantage of the present invention is that the
operating conditions are simple to implement and allow the direct
production of the furoic acid derivative of formula (I) free of any
salt, because of the absence of base in the reaction medium.
[0068] The absence of base in the reaction medium also makes it
possible to avoid the degradation of the catalyst support and the
leaching of metal particles in the liquid phase, which renders the
catalyst recyclable for several successive uses in a closed or
stable reactor under flow in open reactor.
[0069] The present invention also provides a composition comprising
at least furfural and supported gold nanoparticles.
[0070] According to an alternative embodiment, this composition
also contains a furfural derivative of formula (II) and, if
appropriate, water.
[0071] Advantageously, the composition is non-alkaline.
[0072] Method According to the Invention
[0073] Definition of Gold Nanoparticles
[0074] The gold nanoparticles that are suitable for the invention
are well known and are already commonly used in chemistry as
catalysts for reactions of the hydrogenation or oxidation type as
well as, in particular, in optics, electronics, pharmacology,
diagnostics or therapy.
[0075] For most of these applications, the nanoparticles are
attached to a solid support.
[0076] Various methods are known for the preparation of gold
nanoparticles, in particular in a confined mineral medium or in a
confined organic medium.
[0077] The preparation of gold nanoparticles in a confined
inorganic medium may be carried out in inorganic suspensions
(titanium, silica, clay), by reduction of a gold precursor in the
presence of a catalyst such as that described by K. Nakamura et al.
(J. Chem. Eng. Jap., 2001, 34, 1538-1544). The preparation of gold
nanoparticles in a silica matrix bearing hydroxyl groups by
spontaneous reduction of a gold precursor is described by P.
Mukherjee et al. (Chem. Mater., 2002, 14, 1678-1684), and by T.
Yokohama et al. (Journal of Colloid and Interface Science, 2001,
233, 112-116).
[0078] The gold nanoparticles that are suitable for the invention
have a size of between 3 nm and 15 nm, preferably between 5 nm and
10 nm.
[0079] As stated above, the gold particles are supported.
[0080] By way of illustration of the supports which are suitable
for the invention, mention may be made, in particular, of zirconium
dioxide (ZrO.sub.2) and hydrotalcite.
[0081] Thus, according to one embodiment, a catalyst that is
suitable for the invention is gold supported on zirconium dioxide
or on hydrotalcite.
[0082] According to a particular embodiment, the catalyst used is
gold supported on zirconium dioxide.
[0083] The percentage by weight of gold in the Au/ZrO.sub.2
catalyst for the oxidation of furfural is between 1% and 7% by
weight, and is preferably equal to 3% by weight, wherein zirconium
dioxide is used as the support with a low specific surface of less
than or equal to 10 m.sup.2/g.
[0084] As demonstrated in the experimental part below, this
percentage of 3% by weight makes it possible to obtain optimum
selectivity.
[0085] A relatively low percentage by weight of gold makes it
possible to disperse the gold on the ZrO.sub.2 surface and to
increase the amount of active sites. For higher percentages, the
formation of gold aggregates on the surface is possible, which may
result in the formation of a less active catalyst.
[0086] When the catalyst used is Au/ZrO.sub.2, the molar ratio of
furfural/Au for the oxidation of furfural is between 6 and 34, and
preferably this molar ratio is 6.
[0087] According to another particular embodiment, the catalyst
used is gold supported on hydrotalcite.
[0088] The percentage by weight of gold in the Au/hydrotalcite
catalyst for the oxidation of furfural is between 1% and 3% by
weight, and is preferably equal to 2% by weight, wherein
hydrotalcite is used as the support, with a low specific surface of
less than or equal to 10 m.sup.2/g.
[0089] As explained in the examples below, this percentage of 2% by
weight makes it possible to obtain not only a high yield but also
high selectivity in furoic acid.
[0090] When the catalyst used is Au/hydrotalcite, the furfural/Au
molar ratio for the oxidation of furfural is between 22 and 50,
preferably this molar ratio is 22.
[0091] The supported catalyst according to the invention may be
prepared by any conventional method.
[0092] For example, a supported catalyst according to the invention
may be prepared by dissolving a required amount (24.8 mg) of
chloroauric acid hydrate (also called tetrachloroauric acid
hydrate), in particular that sold under the name HAuO.sub.4 by the
company Alpha Aesar in a suitable amount of water (20 ml). Other
gold salts may also be used for this type of preparation, such as
nitrates, especially Au(NO.sub.3).sub.3 or chlorides such as in
particular AuCl.sub.3 or Au.sub.2Cl.sub.6.
[0093] Then a suitable amount (1 g) of support such as zirconium
dioxide or hydrotalcite is added to this solution and the mixture
is stirred at a temperature between 25.degree. C. and 50.degree.
C., preferably at room temperature (25.degree. C.) for a period of
at least 10 minutes.
[0094] Then, an amount (2 ml) of hydrazine (N.sub.2H.sub.4), for
example that marketed in 78-82% aqueous solution by Sigma Aldrich
(hydrazine hydrate) is injected into the solution. The reduction of
gold is then effected spontaneously.
[0095] The solution is subsequently subjected to stirring for a
period of between 30 and 60 minutes, preferably for 40 minutes at a
temperature of between 25.degree. C. and 50.degree. C., preferably
at room temperature (25.degree. C.) until it obtains a precipitate
which is filtered and then washed appropriately.
[0096] The catalyst is obtained in solid form and then dried in an
oven at a temperature between 60.degree. C. and 100.degree. C.,
preferably at 80.degree. C., for a period of between 6 and 14
hours, preferably overnight.
[0097] An example of preparation of a catalyst that is suitable for
the invention is more particularly described in Example 1
below.
[0098] Reaction Conditions
[0099] The oxidation may be carried out in any manner known to
those skilled in the art, in particular under oxygen or air
pressure, preferably under oxygen pressure.
[0100] Preferably, the oxygen or air pressure used is such that the
molar ratio 02/furfural derivative of formula (II) is greater than
2.
[0101] The pressure may especially be 10 to 20 bar (1010.sup.5 to
2010.sup.5 Pa) of air, preferably 15 bar (1510.sup.5 Pa) of
air.
[0102] The oxygen partial pressure may be from 5 to 20 bars (i.e.
510.sup.5 to 2010.sup.5 Pa), preferably from 10 to 15 bars
(1010.sup.5 to 1510.sup.5 Pa), more particularly 15 bars
(1510.sup.5 Pa).
[0103] Typically, the reaction temperature for the oxidation of the
furfural derivative of formula (II), in particular furfural, is
between 70.degree. C. and 150.degree. C., in particular between
90.degree. C. and 120.degree. C., and preferably 110.degree. C.
[0104] However, a temperature above 120.degree. C. is not indicated
insofar as it is likely to cause the degradation of the furfural
and/or the product, the formation of various carbon compounds, and
a decrease in the carbon balance of the reaction. However, the
deposition of carbon on the metal catalysts may cause deactivation
of the catalyst.
[0105] The duration of the reaction for the oxidation of the
furfural derivative of formula (II), in particular furfural, is
between 1 hour and 15.5 hours, preferably between 2 hours and 4
hours. As detailed in the experimental section below, it was
observed that a reaction time longer than 4 hours does not
significantly increase the yield of this reaction and after a
period of 15.5 hours, the furfural becomes unstable and the
quantity of secondary products is no longer negligible.
[0106] The method may be implemented in continuous mode or in batch
mode.
[0107] In an advantageous embodiment mode, the method according to
the invention is implemented in batch mode.
[0108] In general, the method according to the invention may be
applied industrially to the oxidation of furfural and its
derivatives to obtain the corresponding carboxylic acid free of any
salt.
[0109] The expressions "comprised between . . . and . . . " and
"from . . . to . . . " are to be understood as inclusive terms,
unless otherwise specified.
[0110] The examples which follow will make it possible to better
understand the invention, without, however, being limiting in
nature.
EXAMPLES
Example 1: Preparation of Catalysts Suitable for the Invention
[0111] a) Catalyst 3% Au/ZrO.sub.2
[0112] 66.5 mg of chloroauric acid hydrate (Au 49% min., from the
company Alpha Aesar, 99.9%) are dissolved in 20 ml of water. 997 mg
of zirconium dioxide, monoclinic with a baddeleyite structure from
Sigma Aldrich, are added to this solution. The mixture is then
stirred at room temperature (25.degree. C.) for 10 minutes.
[0113] 2 ml of hydrazine (N.sub.2H.sub.4, 80% aqueous solution,
from Sigma Aldrich) are then injected into the solution. The
reduction of gold then takes place spontaneously.
[0114] The solution is stirred for 40 minutes at room temperature
(25.degree. C.) until a purple precipitate is obtained. The
precipitate thus obtained is then filtered under vacuum and washed
3 times with water (3 times 20 ml) and once with acetone (20
ml).
[0115] The solid thus obtained is subsequently dried overnight in
an oven at 80.degree. C.
[0116] b) Catalyst 2% Au/hydrotalcite
[0117] 44.4 mg of chloroauric acid hydrate (Au 49% min., from the
company Alpha Aesar, 99.9%) are dissolved in 20 ml of water. 912 mg
of hydrotalcite synthesized in the laboratory with a low specific
surface area of 10 m.sup.2/g are added to this solution. The
mixture is then stirred at room temperature (25.degree. C.) for 10
minutes.
[0118] 2 ml of hydrazine (N.sub.2H.sub.4, 80% aqueous solution,
from Sigma Aldrich) are then added to the solution. The reduction
of gold then takes place spontaneously.
[0119] The solution is stirred for 40 minutes at room temperature
(25.degree. C.) until a purple precipitate is obtained. The
precipitate thus obtained is then filtered under vacuum and washed
3 times with water (3 times 20 ml) and once with acetone (20
ml).
[0120] The solid thus obtained is subsequently dried overnight in
an oven at 80.degree. C.
Example 2: General Procedure for the Oxidation of a Furfural
Derivative of Formula (II) and More Particularly of Furfural
[0121] The procedure detailed below is the general procedure used
for the catalytic tests whose results are set forth in Example 3 of
the present invention.
[0122] The catalytic tests are carried out in a 50 ml autoclave
reactor equipped with a thermocouple (Top Industrie Autoclave
2456). The procedure for a standard test is detailed below.
[0123] The amount is adjusted according to the test to be
performed, for example 50 mg (from 10 to 150 mg) of furfural are
added to distilled water (10 ml) and stirred magnetically for 10
minutes. 9 ml of the furfural solution are then added to the
autoclave reactor under atmospheric pressure and at room
temperature (25.degree. C.).
[0124] 100 mg of catalyst (variable nature according to the test
carried out) are then added to the reaction mixture at ambient
temperature (25.degree. C.). The catalysts suitable for the
invention to be tested, namely Au/ZrO.sub.2 and Au/hydrotalcite are
those prepared according to the protocol of Example 1.
[0125] 10 ml of distilled water are again added to the reactor at
ambient temperature (25.degree. C.). The reactor is then closed and
the magnetic stirring is set at 900 rpm at room temperature
(25.degree. C.). Then, the reactor is purged three times with
oxygen. The 02 pressure is then set at 1510.sup.5 Pa (15 bar) and
the reactor is closed. The temperature is then set to the desired
value according to the test to be performed, namely 90.degree. C.,
110.degree. C. and 120.degree. C., as indicated in the examples
below.
[0126] The reaction time imposed for these tests may also be
variable depending on the parameter tested, as specified below; it
may be 1 hour, 2 hours, 4 hours or 15.5 hours.
[0127] Then, the reactor is cooled to room temperature (25.degree.
C.) and the resulting solution is taken from the reactor,
centrifuged to separate it from residual solid catalyst particles
and analyzed by HPLC (high performance liquid chromatography) whose
protocol is detailed below.
[0128] HPLC Analysis
[0129] The reaction mixture is filtered using an HPLC filter (2.5
.mu.m), and then diluted 5 times with water. The analysis by liquid
chromatography is carried out on a Shimadzu UFLC-MS 20-20 HPLC
chain equipped with a Phenomenex Synergi 2.5 .mu.m Hydro-RP 100 A
column. The column is purged at 0.5 ml/min at room temperature.
(25.degree. C.) with a 0.1% trifluoroacetic acid aqueous solution
as the mobile phase, for 12 minutes. The retention times for each
compound are verified using commercial standards. The conversion,
yields and selectivity are determined by the calibration curve
method (performed for each compound).
[0130] The conversions are calculated as follows:
Furfural Tinitial - Furfural Tfinal Furfural Tinitial .times. 100
##EQU00001##
[0131] While the yield is calculated as follows:
Product Tfinal Furfural Tinitial .times. 100 ##EQU00002##
[0132] The reaction rate is calculated as follows:
Furfural Tinitial - Furfural Tfinal ( mmol ) time ( min ) weightAu
( mg ) ##EQU00003##
Example 3: Catalytic Performance Observed with a Supported Catalyst
Based on Gold
[0133] 3.1 Influence of Temperature
[0134] The oxidation method as described above is carried out with
the Au/ZrO.sub.2 catalyst according to the invention as synthesized
as an example 1a). The percentage by weight of gold in this
catalyst is 3% by weight.
[0135] The O.sub.2 pressure, the stirring speed and the amount of
catalyst imposed are those indicated in Example 2. The amount of
furfural used is 50 mg, and the reaction time is 1 hour.
[0136] The reaction temperatures tested are 90.degree. C.,
110.degree. C. and 120.degree. C.
[0137] For each of these reaction temperatures, the conversion rate
of furfural, furoic acid yield, furoic acid selectivity and carbon
balance are summarized in Table 1 below.
TABLE-US-00001 TABLE 1 Furfural Yield in Selectivity in Carbon
Temperature conversion rate furoic acid furoic acid balance
.degree. C. (%) (%) (%) (%) 90 10.7 6.1 57.5 95.5 110 35.0 29.7
84.7 95.0 120 46.0 36.5 79.2 90.4
[0138] It appears that the best selectivity is observed with a
reaction temperature of 110.degree. C.
[0139] 3.2 Influence of Au Concentration
[0140] A preliminary test, excluding the invention, is carried out
in the presence of ZrO.sub.2 alone, i.e. without gold
nanoparticles. It should be noted that the oxidation reaction of
furfural does not occur.
[0141] Then, the oxidation method as described above is carried out
with the Au/ZrO.sub.2 catalyst according to the invention. Four
different percentages by weight of gold were tested for this
catalyst, namely 1%, 3%, % 5% and 7% by weight. The catalysts are
prepared according to the synthesis protocol described in Example
1a), optionally adapted according to the desired weight
percentage.
[0142] The required O.sub.2 pressure, stirring rate and catalyst
amount are as indicated in Example 2. The amount of furfural used
is 50 mg, the reaction temperature is 110.degree. C., and the
reaction time is 4 hours.
[0143] For each of the percentages by weight of gold, the molar
ratio of furfural/Au, the conversion rate of furfural, the yield in
furoic acid, the selectivity of furoic acid and the carbon balance
are summarized in Table 2 below.
TABLE-US-00002 TABLE 2 Furfural/ Furfural con- Yield in Selectivity
in Carbon Au molar version rate furoic acid furoic acid balance
Catalyst ratio (%) (%) (%) (%) 1% 100 7.0 3.9 55.5 96.9
Au/ZrO.sub.2 3% 30 35.0 29.7 84.7 95.0 Au/ZrO.sub.2 5% 20 45.1 35.4
78.5 90.3 Au/ZrO.sub.2 7% 14 38.8 32.1 82.7 93.3 Au/ZrO.sub.2
[0144] It appears that when the gold load increases, the conversion
to furfural also increases, but, at the same time, the impact on
the selectivity is rather limited, at least for loads greater than
3% by weight.
[0145] The best selectivity is observed with Au/ZrO.sub.2 3% by
weight.
[0146] 3.3 Influence of the Reaction Time
[0147] The oxidation method as described above is carried out with
the Au/ZrO.sub.2 catalyst according to the invention as synthesized
as in example 1a). The percentage by weight of gold in this
catalyst is 3% by weight.
[0148] The O.sub.2 pressure, the stirring rate and the amount of
catalyst imposed are those indicated in Example 2. The amount of
furfural used is 50 mg, and the reaction temperature is 110.degree.
C.
[0149] The reaction times tested are 1 hour, 2 hours, 4 hours and
15.5 hours.
[0150] For each of these times, the conversion rate of furfural,
yield and selectivity (named Select) in furoic acid, secondary
products such as 2(5H)-furanone, maleic acid, and carbon dioxide as
well as the carbon balance are summarized in Table 3 below.
TABLE-US-00003 TABLE 3 Duration (h) 1 2 4 15.5 Conversion (%)
Conversion (%) Conversion (%) Conversion (%) Furfural 35.0 51.7
68.0 91.9 conversion rate (%) Yield Select Yield Select Yield
Select Yield Select (%) (%) (%) (%) (%) (%) (%) (%) Furoic 29.7
84.7 45.0 87.0 54.1 79.6 50.0 54.5 acid 2(5H)furanone 0.2 0.4 0.9
1.7 1.4 2.1 8.5 9.2 Maleic 0.1 0.5 0.4 0.7 0.4 0.6 2.5 2.7 acid
Carbondioxide 0.0 0.0 0.2 0.3 0.2 0.3 1.4 1.5 Carbon 95.0 94.6 87.9
69.1 balance (%)
[0151] Too long reaction times have revealed the instability of
furfural. After 2 hours, the carbon balance and the selectivity in
furoic acid decrease. After a period of 15.5 hours, these decreases
are even greater and the amount of secondary products
simultaneously increases.
[0152] 3.4 Influence of the Nature of the Support
[0153] The oxidation method as described above is carried out with
different catalysts based on gold nanoparticles, namely
Au/CeO.sub.2, Au/MgO, Au/hydrotalcite as synthesized as Example 1
b) and Au/ZrO.sub.2. as synthesized as an example la). The
Au/CeO.sub.2 and Au/MgO catalysts according to the invention may be
prepared by any method known to those skilled in the art and in
particular according to those described in example 1 above. The
percentage by weight of gold in these catalysts is 2% or 3% by
weight, as specified in Table 4 below.
[0154] The required O.sub.2 pressure, stirring rate and catalyst
amount are as shown in Example 2. The reaction temperature is
110.degree. C. and the reaction time is 2 hours.
[0155] As for the amount of furfural used, it is 50 mg.
[0156] For each of these catalysts, the conversion rate of
furfural, the yield and selectivity in furoic acid, and the carbon
balance are summarized in Table 4 below.
TABLE-US-00004 TABLE 4 Furfural Yield in Selectivity in conversion
rate furoic acid furoic acid Carbon Support (%) (%) (%) balance 3%
Au/CeO.sub.2 56.6 38.4 67.8 84.3 according to the invention 3%
Au/MgO 33.1 8.8 26.5 75.7 according to the invention 2% 78.5 71.8
91.4 93.3 Au/hydrotalcite according to the invention 3%
Au/ZrO.sub.2 51.7 45.0 87.0 94.6 according to the invention
[0157] It appears that low activity is observed in the case of Au
supported on CeO.sub.2 or MgO.
[0158] A comparison between the catalytic tests carried out with
different supports shows that, by using a supported catalyst of the
hydrotalcite type, much better performances are obtained (higher
conversion and selectivity).
[0159] 3.5 Influence of the Molar Ratio Furfural/Au
[0160] 3.5.1 Catalyst Au/ZrO.sub.2 According to the Invention
[0161] The oxidation method as described above is carried out with
the Au/ZrO.sub.2 catalyst according to the invention as synthesized
as an Example 1a). The percentage by weight of gold in this
catalyst is 3% by weight.
[0162] The O.sub.2 pressure, the stirring speed and the amount of
catalyst imposed are those indicated in Example 2. The reaction
temperature is 110.degree. C. and the reaction time is 4 hours.
[0163] As for the amount of furfural used, it is adjusted to obtain
three furfural/Au molar ratios of 34, 18 and 6 respectively.
[0164] For each of these ratios, the conversion rate of furfural,
yield and selectivity in furoic acid, and the carbon balance are
summarized in Table 5 below.
TABLE-US-00005 TABLE 5 Furfural Yield in Selectivity in Furfural/Au
conversion rate furoic acid furoic acid Carbon molar ratio (%) (%)
(%) balance 34 68.0 54.1 79.6 87.3 18 78.4 66.1 84.2 89.5 6 87.8
76.6 87.3 90.0
[0165] From these results, it appears that the Furfural/Au molar
ratio has a strong influence on performance.
[0166] In fact, the lower the molar ratio, the higher the
conversion, the selectivity and, therefore, the yield in furoic
acid are high.
[0167] 3.5.2 Au/Hydrotalcite Catalyst According to the
Invention
[0168] The oxidation method as described above is carried out with
the Au/hydrotalcite catalyst according to the invention as
synthesized in Example 1b). The percentage by weight of gold in
this catalyst is 2% by weight.
[0169] The O.sub.2 pressure, the stirring speed and the amount of
catalyst imposed are those indicated in Example 2. The reaction
temperature is 110.degree. C. and the reaction time is 2 hours.
[0170] As for the amount of furfural used, it is adjusted to obtain
a furfural/Au molar ratio of 22.
[0171] The conversion rate of furfural, yield and selectivity in
furoic acid, and the carbon balance are summarized in Table 6
below.
TABLE-US-00006 TABLE 6 Furfural/Au molar ratio 22 Conversion (%)
Furfural 98.2 Yield (%) Selectivity (%) Furoic acid 96.7 98.5
Carbon balance 98.5
[0172] Thus, the use of a 2% by weight Au/hydrotalcite catalyst
makes it possible to obtain a high yield of furoic acid with a high
selectivity.
Example 4: Plasma Analyses Induced Possible Losses of Metal
Residues
[0173] Induced plasma analyses (ICP) of the reaction solution for
the tests (catalytic tests carried out with the 3% Au/ZrO.sub.2
catalyst according to the invention as synthesized in Example 1a)
after 1 and 15.5 hours confirmed that no loss of metal residues
occurred during the reaction.
[0174] ICP optical emission spectrometry measurements (ICP-OES) are
performed on an Agilent 720-ES spectrometer. The samples are
prepared by digestion using aqua regia. The amount of gold in the
solution is determined using the calibration curves obtained with
the standard commercial solutions.
[0175] Table 7 below summarizes the data collected, including the
mean intensity and RSD intensity (Relative Standard Deviation,
coefficient of variation) after 1 hour (white) and 15.5 hours of
reaction (catalytic test).
TABLE-US-00007 TABLE 7 Au 211,068 White = reference (after 1 hour
of reaction) Average intensity 14,286 Intensity % RSD 26,781
Measured after 15.5 hours of reaction Average intensity 12,123
intensity % RSD 50.195 Intensity/white intensity ratio 0.85
* * * * *